My guess is that you installed your gems using sudo (e.g. sudo gem install rails). When you use sudo to install, RVM is being ignored and the system ruby is being used.

When using RVM, you really don't want to install with sudo (note there is a command rvmsudo, to run your RVM setup through sudo, but you really rarely will use this). As you can see from your environment, your gems will be stored in /home/josh/.rvm/gems/ruby-1.9.2-rc2@rails3tutorial/gems, where you do not need root permissions to install.